34 A Comparison of Retrieved Mass-Diameter Relationships in Snowfall from Radar and Ice Water Content Measurements

Tuesday, 15 September 2015
Oklahoma F (Embassy Suites Hotel and Conference Center )
George Duffy, University of Illinois, Urbana, IL; and S. Nesbitt and G. McFarquhar

Mass to diameter (m-D) relationships for ice particles in the form aDb are used to compute bulk microphysical properties, such as radar reflectivity (Z) and Ice Water Content (IWC) from particle size distributions (PSDs). The a and b values required to compute Z and IWC should be common properties of the PSD, but parameters retrieved from Z and IWC measurements tend to produce inconsistent results, and the parameters retrieved from one bulk property can not adequately recreate the measurement of another. In this study, we compare a and b mass parameters retrieved from collocated PSD, Z, and IWC measurements of synoptic snowstorms during three days of the Global Precipitation Measurement (GPM) Cold Season Experiment (GCPEx). Five-second PSD averages are collected by a Cloud Imaging Probe and a High Volume Precipitation Spectrometer aboard the University of North Dakota UND Citation. IWC is inferred from a Nevzorov Total Water Content probe in regions with minimal liquid water, as detected by a King Liquid Water Content probe. Reflectivity measurements come from a ground based WKR C-Band radar and are matched to Citation measured PSDs within a ±three minute window and a <500 meter radius of influence. Parameter a tends to decrease with the bth moment of the PSD, and this relationship gets steeper with increasing values of b. The difference between mass parameter a retrieved from Z and IWC methods varies with b and is minimized around b=2.3. Implications for improved remote sensing retrievals of IWC will be discussed.
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